718 REPORT — 1898. 



progress and date of meduUation of the various fibres of the cranial, 

 spina], and sympathetic nerves. 



Afferent fibres have been distinguished from efferent by the use of 

 the Wallerian method, and the number of afferent fibres in various 

 somatic and sympathetic branches has been determined in kittens from 

 a few days to several weeks old. At the same time the intra-spinal 

 degeneration resulting from section of posterior roots in kittens of 

 different ages has been traced by Marchi's method. By these observa- 

 tions an attempt has been made to divide the fibres of all the peripheral 

 nerves into embryological systems, and to trace the distribution of each 

 afferent and efferent system separately. 



Several experiments have also been performed according to V. 

 Gudden's method upon kittens and rabbits a few days old to determine — 

 (1) the effect upon the development of a posterior root ganglion of section 

 of the corresponding posterior roots or peripheral nerve trunk respec- 

 tively ; (2) the changes produced in certain posterior rootlets, spinal 

 ganglia, and cells of the spinal cord by cutting many peripheral branches, 

 each of which contains a relatively large proportion of fibres belonging 

 to a given embryological system ; (3) the effect upon the development of 

 the fibres of the cervical sympathetic nerve of section of the nerve itself, 

 or of branches of the superior cervical sympathetic ganglion ; (4) the 

 central origin of the fibres of the cervical sympathetic nerve by the 

 atrophy of cells following section of the nerve in very early life ; and 

 (5) the alterations in the cells of a sympathetic ganglion resulting from 

 section of its pr?e- or post-ganglionic fibres respectively. 



I append a summary of some of the observations made : 



The two systems of afferent fibres, which are the first to become 

 meduUated, are found to be common to both the somatic and sympathetic 

 nerves, and to assume their fatty sheath before the efferent visceral fibres. 

 The two afferent systems mentioned are distinguished from each other, 

 not only by the considerable interval between the dates of their meduUa- 

 tion, but also by the mode of their peripheral termination, the fibres of 

 the earliest medullated system alone entering end-organs. The later 

 meduUated afferent fibres of both somatic and sympathetic nerves have 

 not yet been fully investigated. 



The efferent somatic fibres do not all become medullated at the same 

 time, and certain embryological relations have been observed between 

 certain cranial and spinal efferent fibres. The various visceral efferent 

 fibres also develop their medulla at different dates. 



Section of the posterior roots in very young animals has little, if any, 

 effect upon the development of the corresponding posterior root ganglion, 

 but section of the trunk of the nerve distal to the ganglion causes marked 

 macroscopic and microscopic changes in the same duration of experiment, 

 viz., about eight weeks. These results confirm the work of Lugaro upon 

 the spinal ganglia of adult animals. In the second form of experiment 

 ' obvious changes are found, also in the posterior roots, and it is possible 

 by this method to connect certain posterior root fibres with given afferent 

 nerves. 



Early section of the cervical sympathetic nerve markedly hinders the 

 development of the fibres of that nerve, and though some fibres become 

 eventually medullated, they are small, and stain only a faint grey colour 

 with osmic acid. In two kittens in which the internal carotid branches 

 of the superior cervical sympathetic ganglion had been cut some days 



